Wiring Board and Production Method Thereof

ABSTRACT

It is an object of the present invention to provide a wiring board having high-density wiring with a controlled shape without masking by a resist film and a production method thereof. In the present invention, the production method of a wiring board having copper wiring on an insulating substrate includes the steps of forming a metal seed layer on the insulating substrate, the metal seed layer having a roughened shape in a portion on which the copper wiring or a bump is to be formed, and forming an electroplated film of copper or an alloy of copper through electroplating on the portion of the metal seed layer having the roughened shape. A substance for suppressing the plating reaction is added to a plating bath to provide an angle of 90 degrees or smaller between a surface of the insulating substrate and a side of the electroplated film.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. application Ser.No. 11/205,175 filed Aug. 17, 2005, the contents of which areincorporated herein by reference. This application is related to U.S.patent application Ser. No. 11/340,570, filed Jan. 27, 2006.

INCORPORATION BY REFERENCE

The present application claims priority from Japanese applicationJP2005-019437 filed on Jan. 27, 2005, the content of which is herebyincorporated by reference into this application.

BACKGROUND OF THE INVENTION

The present invention relates to a wiring board having a wiring made ofcopper or an alloy of copper, and to a production method thereof.

Electronic devices with smaller size, lighter weight, and lower cost areneeded increasingly year after year. This requires wiring boards used inthose electronic devices to have high-density wiring formed with lowcost in order to achieve smaller size and lighter weight. Productionmethods of wiring boards can be broadly classified into two: asubtractive method and an additive method. In the subtractive method, anetching resist is formed on a copper foil applied to a substrate and thecopper is etched away except the portions which will serve as wiring,thereby forming wiring. In the additive method, a resin substrate iscovered with a plating resist film except the portions which will serveas wiring and a plated film is formed only in the portions which willserve as wiring.

In the conventional production methods of wiring boards, both of thesubtractive method and additive methods require the masking of thesubstrate surface by the resist. The masking by the resist film needsthe steps of film formation, exposure, and development. These stepsinvolve high cost due to the use of chemicals and the treatment of wasteliquid. In addition, the large number of the steps cause a longprocessing time. Thus, the process of masking by the resist film hasbeen a bottleneck in producing wiring boards with low cost in a shorttime.

As a solution therefor, production methods of wiring boards have beenstudied which use no masking by a resist. One of them is a known methodin which a metal seeding solution layer is formed on a substrate surfaceand exposed to light at an appropriate wavelength to form a metal seedlayer and then plating or the like is performed to form a metal film(for example, JP-A-7-336018). In another known method, a plate is usedto form a chemically changed pattern on a substrate surface andelectroless plating is performed to form wiring (for example,JP-A-2002-184752).

The conventional methods for forming a wiring board without masking by aresist have the following problem. For example, the method in which ametal seeding solution layer is formed on a substrate surface andexposed to light to form a metal seed layer and then plating or the likeis performed to form a metal film has difficulty in forming wiring withhigher density since the shape of the plated film serving as wiring isnot sufficiently considered. The reason thereof is as follows. Whenplating is performed without using a resist film, the plated film isisotropically grown from the seed layer. The isotropically grown platedfilm creates a semicircular cross-section in the plated wiring to occupya larger area on the wiring board as compared with rectangular wiringhaving the same sectional area. Therefore, the wiring with thesemicircular cross-section is disadvantageous in providing higherdensity as compared with the rectangular wiring.

In the method in which a plate is used to form a chemically changedpattern on a substrate surface and electroless plating is performed toform wiring, the shape of the plated film serving as the wiring is notconsidered sufficiently. When plating is performed without using aresist, the plated film has a larger width than the seed layer, which isdisadvantageous in achieving higher density in wiring. In addition, thewiring cannot be formed with a width as designed in the underlying film.

Thus, it is an object of the present invention to provide a wiring boardhaving high-density wiring with a controlled shape without masking by aresist and a production method thereof.

SUMMARY OF THE INVENTION

According to the present invention, a method of producing wiring boardincludes the steps of forming a metal seed layer on an insulatingsubstrate, the metal seed layer having a roughened area on which copperwiring or a bump is to be formed, and forming an electroplated film ofcopper or an alloy of copper through electroplating on the roughenedarea of the metal seed layer. A substance for suppressing platingreaction is added to a plating bath to provide an angle of 90 degrees orsmaller between a surface of the insulating substrate and a side of theelectroplated film.

According to the present invention, a wiring board includes a metal seedlayer on an insulating substrate, the metal seed layer having aroughened area thereon, and wiring or a bump made of copper or an alloyof copper formed through electroplating on the portion of the metal seedlayer having the roughened area. An angle between a surface of theinsulating substance and a side of the wiring or bump is 90 degrees orsmaller.

The present invention allows high-density wiring with a controlled shapeto be formed without using a resist. The angle between the wiring sideand the substrate surface set to 90 degrees or smaller enables theformation of the wiring through electroplating without reducing thedimensional accuracy of the wiring.

Other objects, features and advantages of the invention will becomeapparent from the following description of the embodiments of theinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1( a), 1(b) and 1(c) are sectional views showing an example of aproduction method of a wiring board according to the present invention.

FIGS. 2( a), 2(b) and 2(c) are sectional views showing another exampleof the production method of a wiring board according to the presentinvention.

FIGS. 3( a), 3(b), 3(c) and 3(d) are sectional views showing yet anotherexample of the production method of a wiring board according to thepresent invention.

FIGS. 4( a), 4(b), 4(c) and 4(d) are sectional views showing stillanother example of the production method of a wiring board according tothe present invention.

FIGS. 5( a), 5(b), 5(c) and 5(d) are sectional views showing a furtherexample of the production method of a wiring board according to thepresent invention.

FIGS. 6( a), 6(b), 6(c), 6(d) and 6(e) are sectional views showing astill further example of the production method of a wiring boardaccording to the present invention.

FIGS. 7( a), 7(b), 7(c), 7(d), 7(e) and 7(f) are sectional views showinga yet further example of the production method of a wiring boardaccording to the present invention.

FIGS. 8( a), 8(b), 8(c) and 8(d) are sectional views showing anotherexample of the production method of a wiring board according to thepresent invention.

FIG. 9 shows an evaluation method of the sectional shape of wiring.

FIGS. 10( a), 10(b) and 10(c) are sectional views showing the sectionalshapes of wiring provided in Examples of the present invention.

FIG. 11 is a plan view showing a wiring board viewed from anelectroplated copper film.

DETAILED DESCRIPTION OF THE INVENTION

The present inventors have found that an appropriate roughened area isformed on a metal seed layer for electroplating and plating conditionsare optimized to allow the controlled deposition shape of the platedfilm in the portion having the roughened area. An effective approach tocontrol of the deposition conditions of the plated film is to add acompound, as an additive, which suppresses the plating reaction andloses the plating reaction suppressing effect as the plating reactionproceeds. The property of suppressing the plating reaction can be seenfrom the fact that the addition of the additive increases the metaldeposition overpotential. The property of losing the plating reactionsuppressing effect as the plating reaction proceeds can be seen from thefact that the metal deposition rate is decreased with a higher flow rateof a plating bath, that is, with quicker supply of the additive to themetal surface. When the additive loses the plating reaction suppressingeffect, the additive may be decomposed into different substrates, orreduced to a substrate with a different oxidation number.

When plating is performed with the plating bath containing such anadditive, the additive loses its effect on the surface of the metal seedlayer as the plating reaction proceeds, so that the effectiveconcentration of the additive contributing to the plating reactiondecreases. The portion of the metal seed layer of the roughened shapehas a relatively larger surface area to consume the additive at a higherrate as compared with the portion without any roughened shape, whichresults in an even lower concentration of the additive near the surfaceof the metal seed layer of the roughened area. Thus, in the portion ofthe roughened shape on the metal seed layer, the additive effect ofsuppressing the plating reaction is reduced to increase the platingrate. Since the plating rate depends on the concentration of theadditive on the surface of the metal seed layer, the shape of the platedfilm changes with the distribution of the additive concentration.

Since the distribution of the additive concentration can be changed bycontrolling the plating conditions, the shape of the plated film canalso be changed by controlling the plating conditions. The distributionof the additive concentration is provided on the basis of the balancebetween the diffusion of the additive over the metal seed layer and thereaction rate thereof on the surface of the metal seed layer. Thus,controlling either the diffusion of the additive over the metal seedlayer or the reaction rate thereof on the surface of the metal seedlayer enables control of the shape of the plated film in the portion ofthe roughened shape.

The diffusion rate of the additive over the metal seed layer is largelyaffected by the concentration of the additive in the plating bath, andthe reaction rate of the additive on the metal seed layer is largelyaffected by the current density during plating. Thus, changing theadditive concentration in the plating bath or the current density duringthe plating can control the distribution of the additive concentration,thereby making it possible to achieve preferential deposition of theplated film on the roughened area and control of the shape of the platedfilm.

Description will hereinafter be made for aspects of a production methodof a wiring board of the present invention.

According to one aspect, the production method includes the steps offorming the metal seed layer on the insulating substrate, forming therough area on the metal seed layer including the portion on which wiringor a bump is to be formed, forming the electroplated film made of copperor an alloy of copper on the rough area of the metal seed layer throughthe electroplating, and removing the seed metal layer and theelectroplated copper film except their portions having the rough areathereon. The substance for suppressing the plating reaction is added tothe plating bath to provide an angle of 90 degrees or smaller betweenthe surface of the insulating substrate and the side of theelectroplated film.

According to another aspect, the production method includes the steps offorming the metal seed layer having the rough area formed thereon on theinsulating substrate, planarizing the roughened shape on the metal seedlayer except its portion on which the copper wiring or bumps are to beformed, forming the electroplated film made of copper or an alloy ofcopper through the electroplating on the metal seed layer, and removingthe metal seed layer and the electroplated film except their portionshaving the roughened area thereon. The substance for suppressing theplating reaction is added to the plating bath to provide an angle of 90degrees or smaller between the surface of the insulating substrate andthe side of the electroplated film.

According to yet another aspect, the production method includes thesteps of forming the metal seed layer serving as a power supply layerfor the electroplating, forming an insulating film serving as theinsulating substrate on the metal seed layer with a casting method,forming the rough area in a portion of the metal seed layer on whichwiring or a bump is to be formed, forming the electroplated film made ofcopper or an alloy of copper through the electroplating on the portionof the metal seed layer having the rough area, and removing the metalseed layer and the electroplated film except their portions having therough area thereon. The substance for suppressing the plating reactionis added to the plating bath to provide an angle of 90 degrees orsmaller between the surface of the insulating substrate and the side ofthe electroplated film.

In the present invention, an arithmetic average roughness Ra (defined inJIS B0601) of the portion having the rough area of the substrate or themetal seed layer is set to be larger than Ra in the remaining portion.Alternatively, an average length of a roughness curve element RSm(defined in JIS B0601) of the portion having the rough area of thesubstrate or the metal seed layer is set to be smaller than RSm in theremaining portion.

It is desirable that the surface roughness of the portion having therough area of the metal seed layer on which the plated film ispreferentially formed has an arithmetic average roughness Ra (defined inJIS B0601) of 0.01 to 4 μm and has an average length of a roughnesscurve element RSm of 0.005 to 8 μm. More specifically, it is desirablethat the surface roughness of the portion having the roughened shape ofthe metal seed layer has an arithmetic average roughness Ra (defined inJIS B0601) of 0.1 to 1 μm and has an average length of a roughness curveelement RSm of 0.05 to 2 μm.

The substance added to the plating bath desirably increases thedeposition overpotential of the metal deposition through the platingwhen the flow rate of the plating bath to which the substrate is addedincreases. As an example of such a substrate, at least one of cyaninedyes is desirably added. A particularly desirable cyanine dye is acompound shown in the formula below (X represents an anion and nrepresents one of the numbers 0, 1, 2, and 3).

The cyanine dye desirably has a concentration of 3 to 15 mg/dm³. In thepresent invention, at least one substance selected from a polyether, anorganic sulfur compound, and a halide ion can be added to anelectrolytic copper plating bath.

The electrolytic copper plating in forming the copper film is desirablyperformed with a constant current at a current density of 0.1 to 2.0A/dm².

Next, description will be made for aspects of the wiring board of thepresent invention.

According to one aspect, the wiring board has the metal seed layer onthe insulating substrate, the metal seed layer having the rough areathereon, and wiring or bumps formed through electroplating on theportion of the metal seed layer having the rough area. An angle betweena surface of the insulating substance and a side of the wiring or bumpis 90 degrees or smaller. An arithmetic average roughness Ra, defined inJIS B0601, of the portion having the rough area of the substrate or themetal seed layer is larger than an arithmetic average roughness Ra ofthe remaining portion.

According to one aspect, the wiring board has the metal seed layer onthe insulating substrate, the metal seed layer having the rough areathereon, and wiring or bumps of copper or an alloy of copper formedthrough electroplating on the portion of the metal seed layer having therough area. An angle between a surface of the insulating substance and aside of the wiring or bump is 90 degrees or smaller. An average lengthof a roughness curve element RSm, defined in JIS B0601, of the portionhaving the rough area of the substrate or the metal seed layer issmaller than an average length RSm of the remaining portion.

It is desirable that the surface roughness of the portion having therough area of the metal seed layer has an arithmetic average roughnessRa (defined in JIS B0601) of 0.01 to 4 μm, or an average length of aroughness curve element RSm of 0.005 to 8 μm. More specifically, Radesirably has a value of 0.1 to 1 μm and RSm desirably has a value of0.05 to 2 μm. It is most desirable that both of them fall within theabovementioned ranges.

The angle between the surface of the insulating substrate and the sideof the wiring or bump is desirably equal to or larger than one degree.

In the wiring board, the plated copper or an alloy of copper desirablyhas a surface in parallel with the surface of the insulating substrate.

DESCRIPTION OF PREFERRED EMBODIMENTS

Examples of the present invention will hereinafter be described. First,table 1 shows the results of Examples 1 to 22 and Comparative Example 1.

TABLE 1 Additive Concentration Current Density No. Additive Type[mg/dm³] [A/dm⁻²] Ra RSm θ [degree] Example 1 A-2 7.0 1.25 0.01 0.02 83Example 2 A-2 7.0 1.25 0.05 0.04 83 Example 3 A-2 7.0 1.25 0.4 1.1 85Example 4 A-2 7.0 1.25 1.5 1.4 80 Example 5 A-2 7.0 1.25 2.0 4.0 86Example 6 A-2 7.0 1.25 0.5 0.6 83 Example 7 A-2 7.0 1.25 1.0 1.1 89Example 8 A-2 7.0 1.25 0.4 3.1 85 Example 9 A-2 2.5 1.0 0.4 1.1 86Example 10 A-2 5.0 1.0 0.4 1.1 85 Example 11 A-2 7.5 1.0 0.4 1.1 32Example 12 A-2 10 1.0 0.4 1.1 19 Example 13 A-2 7.0 0.50 0.4 1.1 10Example 14 A-2 7.0 1.5 0.4 1.1 89 Example 15 A-2 10 1.25 0.4 1.1 28Example 16 A-2 10 1.37 0.4 1.1 45 Example 17 A-2 10 1.50 0.4 1.1 52Example 18 A-1 7.0 1.25 0.4 1.1 80 Example 19 A-3 4.0 1.25 0.4 1.1 83Example 20 A-4 5.0 1.0 0.4 1.1 79 Example 21 A-1 7.0 1.5 0.4 1.1 68 A-25.0 Example 22 A-2 7.0 1.0 0.4 1.1 34 B-1 100 C-1 2 Comparative A-2 7.01.25 0.007 10 135 Example 1 Various symbols in the columns “AdditiveType” in Table 1 represent the following chemical substances. A-1:2-[(1,3-Dihydro-1,3,3-trimethyl-2H-indol-2-ylidene)-methyl]-1,3,3-trimethyl-3H-indoliumperchlorate A-2:2-[3-(1,3-Dihydro-1,3,3-trimethyl-2H-indol-2-ylidene)-1-propenyl]-1,3,3-trimethyl-3H-indoliumchloride A-3:2-[5-(1,3-Dihydro-1,3,3-trimethyl-2H-indol-2-ylidene)-1,3-pentadienyl]-1,3,3-trimethyl-3H-indoliumiodide A-4:2-[7-(1,3-Dihydro-1,3,3-trimethyl-2H-indol-2-ylidene)-1,3,5-heptatrienyl]-1,3,3-trimethyl-3H-indoliumiodide B-1: Polyethylene glycol (average molecular weight 3000) C-1:bis(3-sulfopropyl)disulfide

EXAMPLE 1

A solution containing dispersed silver particles with an averagediameter of 20 nm was sprayed with an ink jet technique onto a surfaceof an insulating substrate 1 (Kapton EN made by Du Pont-Toray Co., Ltd.)made of polyimide film with a thickness of 25 μm shown in FIG. 1( a) toform a metal seed layer 2 with a wiring width of 20 μm and a thicknessof 0.2 μm as shown in FIG. 1( b). Then, the insulating substrate washeated to a temperature of 200° C. to fuse the silver particles. As theinsulating substrate, it is possible to use not only the polyimide butalso a resin of polyester, class epoxy, phenol, and aramid, ceramics,and glass. As the particles, it is possible to use metal particles ofplatinum, gold, copper, nickel, tin and the like, other than silver. Theroughness on the surface of the metal seed layer formed by the silverparticles was measured with a surface roughness measuring apparatus. Themeasurement showed that the surface roughness of the metal seed layerhad an arithmetic average roughness Ra (defined in JIS B0601) of 0.01 μmand an average length of a roughness curve element RSm of 0.02 μm.

Electroplating was performed immediately after the formation of themetal seed layer to form an electroplated copper film 3 as shown in FIG.1( c). The electroplating was performed by using a plating bath having acomposition shown in Table 2 to which a substrate shown in Table 1 isadded as an additive. The electroplating was performed for 40 minutes ata current density of 1.25 A/dm² with the plating bath at a temperatureof 25° C. Phosphorus copper was used as an anode.

TABLE 2 Component Concentration (g/dm³) Copper Sulfate Pentahydrate  64Sulfuric Acid 180 Chloride Ion 70 × 10⁻³

The cross-section of the wiring board was observed after the plating tomeasure an angle θ between the side wall of the electroplated copperfilm and the polyimide film substrate as shown in FIG. 9, and an angleof 83 degrees was found.

As a result, it was possible to produce the wiring board in which copperwiring having a generally rectangular wiring section is formed on themetal seed layer including the silver particles. It should be noted thatthe plan view of the wiring board viewed from the electroplated copperfilm 3 is as shown in FIG. 11, and this applies to the followingExamples.

EXAMPLE 2

A metal seed layer 2 with a wiring width of 10 μm was formed as shown inFIG. 2( a) through a mask with a sputtering technique on a surface of aninsulating substrate 1 (Upilex S made by Ube Industries Ltd.) made ofpolyimide film with a thickness of 25 μm shown in FIG. 2( a). The metalseed layer was made of two layers: a nickel film with a thickness of0.01 μm formed on the substrate and a copper film with a thickness of0.5 μm formed on the nickel film. As the metal seed layer, it ispossible to use not only the stacked film of nickel and copper but alsoa stacked film of chromium and copper. Then, copper rougheningprocessing was performed to form a roughened shape on the surface of thecopper film as shown in FIG. 2( b). The metal seed layer in FIG. 2( b)is made of the two layers, although not shown. The copper rougheningprocessing was performed by using MultiBond made by Nippon MacDermidCo., Inc. in accordance with steps shown in Table 3. As a solution usedcopper roughening process, it is possible to use MEC etch BOND made byMec Co., Ltd., Circubond made by Shipley Far East Ltd., Alpha Prep madeby Alpha Metals Ltd. and the like, other than the abovementioned one.

TABLE 3 Temperature Time Step Processing Liquid (° C.) (Seconds) 1 5 vol% Sulfuric Acid 25 30 2 Pure Water (Running Water) 22 60 3 2 vol %MB-100B 25 30 2.9 vol % MB-100C 4 5 vol % Sulfuric Acid 32 15 15 vol %MB-100A 2 vol % MB-100B 2.9 vol % MB-100C 5 Pure Water (Running Water)22 60

The rough area on the surface of the copper film after the copperroughening processing was measured with a surface roughness measuringapparatus. The measurement showed that the surface roughness of themetal seed layer had an arithmetic average roughness Ra (defined in JISB0601) of 0.05 μm and an average length of a roughness curve element RSmof 0.04 μm. Electroplating was performed immediately after the formationof the roughened shape on the surface of the copper film in the metalseed layer 2 to form an electroplated copper film 3 as shown in FIG. 2(c). The electroplating was performed by using the same composition of aplating bath and the same plating conditions as those in Example 1. Thecross-section of the wiring board was observed after the plating tomeasure an angle θ between the side wall of the electroplated copperfilm and the polyimide film substrate as shown in FIG. 9, and an angleof 83 degrees was found.

As a result, it was possible to produce the wiring board in which copperwiring having a generally rectangular wiring section is formed on thecopper film formed with the sputtering technique.

EXAMPLE 3

As shown in FIG. 3( a), a nickel film with a thickness of 0.1 μm formedon a surface of an insulating substrate 1 made of glass epoxy resin anda copper film with a thickness of 1.0 μm was formed with the sputteringtechnique on the nickel film. Next, copper roughening processing wasperformed to form a rough area in the portion of the copper surface onwhich wiring was to be formed, thereby providing the shape shown in FIG.3( b). The rough area was formed with sandblast. The sandblast wasperformed by spraying alumina particles onto the copper surface througha mask pattern with a wiring width of 8 μm. The roughened shape on thecopper surface after the sandblast processing was measured with asurface roughness measuring apparatus. The measurement showed that thesurface roughness of the metal seed layer had an arithmetic averageroughness Ra (defined in JIS B0601) of 0.4 μm and an average length of aroughness curve element RSm of 1.1 μm. Electroplating was performedimmediately after the formation of the roughen area on the coppersurface to form an electroplated copper film 3 as shown in FIG. 3( c).The electroplating was performed by using the same composition of aplating bath and the same plating conditions as those in Example 1.Next, a copper etchant (MECBRITE made by Mec Co., Ltd) was used to etchaway the portions of the electroplated copper film 3 and the copper seedlayer on which the rough area was not formed. In addition, MEC REMOVERmade by Mec Co., Ltd was used to remove a portion of the nickel seedlayer to provide the structure shown in FIG. 3( d). The cross-section ofthe wiring board was observed after the plating to measure an angle θbetween the side wall of the copper film and the substrate as shown inFIG. 9, and an angle of 85 degrees was found.

As a result, it was possible to produce the wiring board in which copperwiring having a generally rectangular wiring section is formed on thecopper seed layer having the roughen area formed thereon through thesandblast.

EXAMPLE 4

As shown in FIG. 4( a), a surface of an insulating substrate 1 made ofpolyimide film with a thickness of 25 μm was treated with a surfacemodification solution shown in Table 4 at a temperature of 25° C. fortwo minutes and then plating was performed with an electroless copperplating bath (CUST-2000 made by Hitachi Chemical Co., Ltd.) to form ametal seed layer 2. After the plating, the substrate was washed withrunning water and vacuum drying was performed thereon at 25° C. for twohours. The copper film had a thickness of approximately 300 nm at thatpoint. The roughness on the surface of the copper seed layer after theplating was measured with a surface roughness measuring apparatus. Themeasurement showed that the surface roughness of the metal seed layerhad an arithmetic average roughness Ra (defined in JIS B0601) of 1.5 μmand an average length of a roughness curve element RSm of 1.4 μm.

TABLE 4 Component Concentration (g/dm³) Sodium Hydroxide 100Ethylenediamine 70 Ethanol 100

Next, a solution containing dispersed copper particles was sprayed ontothe metal seed layer 2 except the portion which would serve as wiringwith a width of 10 μm, that is, the portion on which wiring was not tobe formed. Then, annealing was performed in vacuum at 350° C. for 30minutes. The surface roughness of the portion sprayed with the copperparticles was measured with a surface roughness measuring apparatus. Themeasurement showed that the surface roughness had an arithmetic averageroughness Ra (defined in JIS B0601) of 0.005 μm and an average length ofa roughness curve element RSm of 11 μm, which demonstrated that thesurface of the copper film was planarized. FIG. 4( b) shows thestructure at that point.

Next, electroplating was performed to form an electroplated copper film3 as shown in FIG. 4( c). The electroplating was performed by using thesame composition of a plating bath and the same conditions as those inExample 1 except the plating time set to 20 minutes. Then, a copperetchant (MECBRITE made by Mec Co., Ltd) was used to etch away theportions of the electroplated copper film and the copper seed layer inwhich the roughened shape was planarized, thereby providing thestructure shown in FIG. 4( d). The cross-section of the wiring board wasobserved after the plating to measure an angle θ between the side wallof the electroplated copper film and the polyimide film substrate asshown in FIG. 9, and an angle of 80 degrees was found.

As a result, it was possible to produce the wiring board in which copperwiring having a generally rectangular wiring section is formed on thecopper seed layer having the rough area formed thereon.

EXAMPLE 5

Roughening processing was performed on a surface of an insulatingsubstrate 1 made of polyimide film with a thickness of 25 μm shown inFIG. 5( a) to form a rough area as shown in FIG. 5( b). The rougheningprocessing was performed in accordance with steps shown in Table 5. As aroughening liquid, it is possible to use not only a mixed solution ofpotassium permanganate solution and sodium hydroxide but also a mixedsolution of chromic acid and sulfuric acid, a mixed solution of chromicacid and fluoroboric acid and the like.

TABLE 5 Temperature Step Processing Liquid (° C.) Time (Seconds) 1 50g/dm³ Potassium 80 5 Permanganate Solution 1 mol/dm³ Sodium Hydroxide 20.5 vol % Sulfuric Acid 40 5 0.2 vol % Hydroxylamine Sulfate

Next, a solution containing dispersed copper particles with an averagediameter of 10 nm was sprayed onto the surface of the insulatingsubstrate 1 to form a metal seed layer 2 with a wiring width of 30 μmand a thickness of 0.03 μm as shown in FIG. 5( c). The roughness on thesurface of the metal seed film formed by the copper particles wasmeasured with a surface roughness measuring apparatus. The measurementshowed that the metal seed layer had an arithmetic average roughness Ra(defined in JIS B0601) of 2.0 μm and an average length of a roughnesscurve element RSm of 4.0 μm.

Electroplating was performed immediately after the formation of themetal seed layer 2 to form an electroplated copper film 3 as shown inFIG. 5( d). The electroplating was performed by using the samecomposition of a plating bath and the same conditions as those inExample 1. The cross-section of the wiring board was observed after theplating to measure an angle θ between the side wall of the electroplatedcopper film and the polyimide film substrate as shown in FIG. 9, and anangle of 86 degrees was found.

As a result, it was possible to produce the wiring board in which copperwiring having a generally rectangular wiring section is formed on themetal seed layer formed of the copper particles.

EXAMPLE 6

As shown in FIG. 6( a), a mold 4 made of silicon which has a 250 nmpitch protrusion with a width of 250 nm and a height of 400 nm over awidth of 10 μm was pushed onto a surface of an insulating substrate 1made of epoxy resin to form a roughened shape. The mold was pushed ontothe insulating substrate 1 while it was heated to near theglass-transition temperature, thereby softening the epoxy resinsubstrate 1 for deformation to the shape corresponding to the mold.After the insulating substrate 1 and the mold 4 was cooled to 25° C.,the mold 4 was separated from the substrate 1. Thus, the rough area wasable to be formed on part of the surface of the insulating substrate 1as shown in FIG. 6( b). Next, a nickel/chromium film made of nickel andchromium at a ratio of 1:1 was formed with a thickness of 10 nm with thesputtering technique on the surface of the insulating substrate 1. Acopper film was formed thereon with a thickness of 100 nm through achemical vapor deposition technique. The nickel/chromium film and thecopper film constituted a metal seed layer 2. FIG. 6( c) shows thestructure at that point. The observation of the rough area on thesurface of the metal seed layer 2 revealed that the metal seed layer 2maintained the roughened shape of the insulating substrate.

Electroplating was performed immediately after the formation of themetal seed layer 2 to form an electroplated copper film 3 as shown inFIG. 6( d). The electroplating was performed by using the samecomposition of a plating bath and the same conditions as those inExample 1 except the plating time set to 90 minutes. Next, a solutioncontaining sulfuric acid and hydrogen peroxide was used to remove theportions of the electroplated copper film and the copper film of themetal seed layer on which the rough area was not formed. In addition, asolution containing potassium permanganate solution was used to remove aportion of the nickel/chromium film. The cross-section of the wiringboard was observed after the plating to measure an angle θ between theside wall of the electroplated copper film and the substrate as shown inFIG. 9, and an angle of 83 degrees was found.

As a result, it was possible to produce the wiring board in which copperwiring having a generally rectangular wiring section is formed on thecopper seed layer having the roughened shape formed thereon.

EXAMPLE 7

As shown in FIG. 7( a), roughening processing was performed on a surfaceof an insulating substrate 1 made of polyimide film with a mixedsolution of chromic acid and sulfuric acid to form a rough area. Thesurface roughness of the portion having the rough area was measured witha surface roughness measuring apparatus. The measurement showed that thesurface roughness had an arithmetic average roughness Ra (defined in JISB0601) of 1.0 μm and an average length of a roughness curve element RSmof 1.1 μm. Next, as shown in FIG. 7( b), a mold 4 made of silicon whichhas a concave portion with a width of 10 μm was pushed onto the surfaceof the insulating substrate 1 to planarize the roughened shape in theportion on which no wiring was to be formed. The mold was pushed ontothe insulating substrate 1 while it was heated to near theglass-transition temperature, thereby softening the insulating substratefor deformation to the shape corresponding to the mold. During the step,the mold 4 was placed such that its concave portion was out of contactwith the insulating substrate 1. Then, after the insulating substrate 1and the mold 4 was cooled to 25° C., the mold 4 was separated from thesubstrate 1. Thus, the rough area was able to be planarized except partof the surface of the insulating substrate 1 as shown in FIG. 7( c). Thesurface roughness of the portion where the rough area was planarized wasmeasured with a surface roughness measuring apparatus. The measurementshowed that the surface roughness had an arithmetic average roughness Ra(defined in JIS B0601) of 0.006 μm and an average length of a roughnesscurve element RSm of 9 μm.

Next, a nickel/chromium film made of nickel and chromium at a ratio of1:1 was formed with a thickness of 10 nm through the sputteringtechnique on the surface of the insulating substrate 1. A copper filmwas formed thereon with a thickness of 100 nm through the chemical vapordeposition technique. The nickel/chromium film and the copper filmconstituted a metal seed layer 2. FIG. 7( d) shows the structure at thatpoint. The surface roughness of the portion of the metal seed layer 2 onwhich the roughened shape was formed was measured with a surfaceroughness measuring apparatus. The measurement showed that the surfaceroughness had an arithmetic average roughness Ra (defined in JIS B0601)of 1.0 μm and an average length of a roughness curve element RSm of 1.1μm. The measurement demonstrated that the metal seed layer 2 maintainedthe roughened shape of the insulating substrate.

Electroplating was performed immediately after the formation of themetal seed layer 2 to form an electroplated copper film 3 as shown inFIG. 7( e). The electroplating was performed by using the samecomposition of a plating bath and the same conditions as those inExample 1. Next, a solution containing sulfuric acid and hydrogenperoxide was used to remove the portions of the electroplated copperfilm 3 and the copper of the metal seed layer on which the rough areawas not formed. Subsequently, a solution containing potassiumpermanganate solution was used to remove a portion of nickel/chromiumfilm. The cross-section of the wiring board was observed after theplating to measure an angle θ between the side wall of the electroplatedcopper film and the polyimide film substrate as shown in FIG. 9, and anangle of 89 degrees was found.

As a result, it was possible to produce the wiring board in which copperwiring having a generally rectangular wiring section is formed on themetal seed layer having the roughened shape formed thereon.

EXAMPLE 8

As shown in FIG. 8( a), an insulating substrate 1 made of polyimide witha thickness of 25 μm was formed with a casting method on a mat surfaceof a metal seed layer 2 made of electrolytic copper foil with athickness of 8 μm. Next, copper roughening processing was performed toform a rough area in a portion of a surface of the metal seed layer onwhich wiring was to be formed as shown in FIG. 8( b). The roughenedshape was formed with sandblast. The sandblast was performed by sprayingalumina particles onto the surface of the metal seed layer through amask pattern with a wiring width of 10 μm. The roughened shape on thesurface of the metal seed layer after the sandblast processing wasmeasured with a surface roughness measuring apparatus. The measurementshowed that the surface roughness had an arithmetic average roughness Ra(defined in JIS B0601) of 0.4 μm and an average length of a roughnesscurve element RSm of 1.1 μ. Electroplating was performed immediatelyafter the formation of the roughened shape on the copper surface to forman electroplated copper film 3 as shown in FIG. 8( c). Theelectroplating was performed by using the same composition of a platingbath and the same plating conditions as those in Example 1. Next, acopper etchant (MECBRITE made by Mec Co., Ltd) was used to etch away theportions of the electroplated copper film 3 and the copper foil on whichthe rough area was not formed, thereby providing the structure shown inFIG. 8( d). The cross-section of the wiring board was observed after theplating to measure an angle θ between the side wall of the electroplatedcopper film and the polyimide film substrate as shown in FIG. 9, and anangle of 85 degrees was found.

As a result, it was possible to produce the wiring board in which copperwiring having a generally rectangular wiring section is formed on themetal seed layer having the roughened shape formed thereon with thesandblast.

EXAMPLE 9 to 22

As shown in Table 1, wiring boards of Examples 9 to 22 were produced inthe same manner as in Example 3 except the additive concentration andplating current density. The observation of the cross-sections of thewiring boards after plating showed that the angle θ between the sidewall of the electroplated copper film and the substrate as shown in FIG.9 depended on the additive concentration and plating current density,and therefore the angle θ can be controlled by changing thoseconditions. As a result, wiring boards were able to be produced to havewiring or bumps with a rectangular, trapezoidal, or triangular sectionas shown in FIG. 10( a), 10(b), or 10(c). In addition, in Examples 9 to22, the ratio of the height of the side wall of the wiring to the widthof the bottom of the wiring can be set to one or higher and the wiringboards can be produced with high electromigration resistance.

COMPARATIVE EXAMPLE 1

Wiring was formed by performing electroplating in the same manner as inExample 2 except that no roughening processing was performed. Thecross-section of the wiring board was observed after the plating tomeasure an angle θ between the side wall of an electroplated copper filmand a substrate as shown in FIG. 9, and an angle of 135 degrees wasfound. The wiring with a width of 10 μm before the electroplating had awiring width of 18 μm after the electroplating, and short-circuit wasfound.

Since plating can be performed on a fine pattern without masking by aresist, the present invention is applicable not only to the formation ofwiring or bumps but also to the formation of a device mounted on awiring board such as a passive device.

It should be further understood by those skilled in the art thatalthough the foregoing description has been made on embodiments of theinvention, the invention is not limited thereto and various changes andmodifications may be made without departing from the spirit of theinvention and the scope of the appended claims.

1. A method of producing a wiring board having copper wiring on aninsulating substrate, comprising the steps of: forming a metal seedlayer on the insulating substrate, the metal seed layer having aroughened shape in a portion on which the copper wiring is to be formed;and forming an electroplated copper film on the portion of the metalseed layer having the roughened shape through electroplating using aplating bath containing a substance for suppressing plating reaction,wherein the electroplated copper film is formed at an angle of 90degrees or smaller between a surface of the insulating substrate and aside of the electroplated copper film.
 2. The method of producing awiring board according to claim 1, wherein the angle between the surfaceof the insulating substrate and the side of the electroplated copperfilm is adjusted by controlling a current density in performing theelectroplating.
 3. The method of producing a wiring board according toclaim 1, wherein the metal seed layer is formed on the insulatingsubstrate and then the roughened shape is formed thereon, and theelectroplated copper film is formed on the metal seed layer through theelectroplating and then the metal seed layer and the electroplatedcopper film are removed except their portions having the roughened shapethereon.
 4. The method of producing a wiring board according to claim 1,wherein the metal seed layer having the roughened shape formed thereonis formed on the insulating substrate, the roughened shape is planarizedexcept its portion on which the copper wiring or bumps are to be formed,the electroplated copper film is formed through the electroplating onthe metal seed layer, and then the metal seed layer and theelectroplated copper film are removed except their portions having theroughened shape thereon.
 5. The method of producing a wiring boardaccording to claim 1, wherein the metal seed layer serving as a powersupply layer for the electroplating is formed, and then an insulatingfilm serving as the insulating substrate is formed on the metal seedlayer with a casting method, the roughened shape is formed in a portionof the metal seed layer on which wiring or bumps are to be formed, theelectroplated copper film is formed on the metal seed layer through theelectroplating, and the metal seed layer and the electroplated copperfilm are removed except their portions having the roughened shapethereon.
 6. The method of producing a wiring board according to claim 1,wherein an arithmetic average roughness Ra, defined in JIS B0601, of theportion having the roughened shape of the insulating substrate or themetal seed layer is larger than an arithmetic average roughness Ra ofthe remaining portion.
 7. The method of producing a wiring boardaccording to claim 1, wherein an average length of a roughness curveelement RSm, defined in JIS B0601, of the portion having the roughenedshape of the insulating substrate or the metal seed layer is smallerthan an average length RSm of the remaining portion.
 8. The method ofproducing a wiring board according to claim 1, wherein the surfaceroughness of the portion having the roughened shape has an arithmeticaverage roughness Ra, defined in JIS B0601, of 0.01 to 4 μm, and anaverage length of a roughness curve element RSm of 0.005 to 8 μm.
 9. Themethod of producing a wiring board according to claim 1, wherein thesubstance added to the plating bath increases the overpotential of themetal deposition through the electroplating when the velocity of theplating bath containing the substrate to increases.
 10. The method ofproducing a wiring board according to claim 1, wherein at least one ofcyanine dyes is added to the plating bath.
 11. The method of producing awiring board according to claim 10, wherein the cyanine dye is acompound shown in the following formula (where X represents an anion andn represents one of the numbers 0, 1, 2, and 3):


12. The method of producing a wiring board according to claim 10,wherein the cyanine dye has a concentration of 3 to 15 mg/dm³.
 13. Themethod of producing a wiring board according to claim 10, wherein theelectroplating is performed with a constant current at a current densityof 0.1 to 2.0 A/dm².
 14. The method of producing a wiring boardaccording to claim 1, wherein at least one substance selected from apolyether, an organic sulfur compound, and a halide ion is added to theplating bath.